NEUROLAW NOVEMBER IV – Neuroscience and Memories

This is the final article in the Neurolaw November series. If you have not yet done so, I highly recommend that you read the Introduction to Neurolaws written by my colleague Maureen Jacob, as well as the other parts in the series. As described well in her article, the foundation of Neurolaws is a simple question: when and where can a jury, judge, and society of peers judge an individual to be in full control of his or her actions? What if this individual has a brain tumor in their amygdala, causing them to be prone to fits of rage and violent tendencies? Or what if this individual has a gene variant that results in Schizophrenia and they legitimately think that everyone in society is out to kill them; if he or she were to harm another person, can self-defense be used as a plea of innocence?

I recently attended the 2017 Annual Meeting of the Society for Neuroscience in Washington D.C. The most recent advances in neuroscience research were presented over the course of four days in a whirlwind series of lectures, poster sessions, symposiums and casual conversations. In addition to the work on brain tumors and mental illness, I had the opportunity to explore the topic of learning and memory, which is the focus of my own neuroscience research. We are all intimately familiar with our memories. They allow us to recall the previous day’s events when we wake up in the morning, they help us pass difficult exams during our studies and most importantly, they define who we are as people by shaping our personalities and preferences.

Before delving deeply into the implications that memories have on legal cases, I want to first outline the brain region responsible for our wonderful ability to recall explicit facts, such as what we ate for breakfast two days ago or the color of our brother’s suit for his high school prom (or “Abiball”). Nestled almost in the center of our brain is the hippocampus, a structure that resembles a seahorse (in fact, the etymology of hippocampus are the Greek words for horse and sea monster). As part of the limbic system, the hippocampus plays an import role in consolidating short-term memory to long-term memory. Damage to this structure is a telltale sign of Alzheimer’s disease and other forms of dementia. In addition to explicit memory the hippocampus, as well as the entorhinal cortex, is involved in spatial memory, or the ability to navigate our surroundings.

But what about memories tied to strong emotional events in our life, such as the flutters in our stomach as we had our first kiss or the fear we felt listening to reports about the September 11th attacks? Or even the confusion surrounding the more recent Brexit vote? These memories, which are usually evoked by a cue, are due to the activity of a network of neurons mostly in the amygdala, as well as parts of the hippocampus and prefrontal cortex[1]. Although it is well-documented that emotions are tied to the activity of the amygdala, the exact effects of memory retrieval are still a matter for research; for example, why is it that certain emotions evoke familiarity but not specific details of an event[2]? The neural circuitry of emotional memories is less well-defined than that of exact, or episodic, memories.

At the conference in Washington D.C., a poster about the stability of memories caught my attention. Presented by a member of the Frankland Lab, the poster posed two simple questions: how does the neural network affect the stability of stored information and what happens to our memories when new information is added? Using artificial networks that mimic those found in the hippocampus, the presenter showed that either changing the network architecture or adding additional memories had an adverse effect on the retrieval of the original memories. Even more alarmingly, it was found that by increasing the excitability and connectivity of the new memories, there was even worse “forgetting” of the original memories[3]. So in other words, an event like graduating from Bachelor’s studies, which is a monumental achievement, would actually diminish our memory of graduating from high school. Since the authors were using an artificial neural network, the exact mechanism by which this diminishing effect occurs was not known. Nonetheless, the results have profound implications, especially in the legal field where memories and testimony of events are paramount to building a case. Indeed, in a 30 in 30 Briefing Series article, my colleague Adam Friedmann outlined how a similar phenomenon called “cue-dependent forgetting” is utilized in tort law.

So, we know that there is biological, sociological, and now artificial evidence that memories can be manipulated. However, if one were to ask individuals, a majority of the people would claim that their memories are immutable. Normally, this fallacy does not have any ramifications, other than petty bickering between friends and family members. But what happens if memories can not only be replaced by new experiences, but also manipulated so that someone misremembers important facts? And not only does he or she misremember the fact, but becomes convinced that the incorrect memory is actually the truth?

This important question is the foundation of Elizabeth Loftus’ theory. Named after the American cognitive psychologist, Elizabeth Loftus, the theory posits that memories are not always accurate and repressed memories can turn out to be false memories created by the brain. For example, let’s say a terrible robbery occurs at someone’s house, and the police are able to narrow down five men as potential perpetrators. The five men are brought into the police station and the victim of the robbery identifies one of the men and shouts, “I am absolutely positive he is the one who robbed my house!” A trial then commences, the victim again proclaims that the defendant committed the crime, and a verdict of 5 years in prison is handed down by the judge. It is a simple example, to be sure, but in recent project about the United States, it was found that over 300 innocent people were convicted of crimes that they did not commit ( Of those 300 convictions, 75% were later found to be due to faulty eyewitness memory. But that finding came often far too late — some of those people had already served 10, 20, or even 30 years of time behind bars. Their livelihoods were forfeited and relationships with friends, neighbors, and their families ruined beyond repair.

I hope that by now it is clear that our memories are not as reliable as we would like to believe. Throughout our everyday lives, as we experience new emotions and sensory inputs from the world around us, our recollection of prior events changes ever so slightly. In other cases, the addition of new facts and opinions can change how we remember information. And as Christopher Nolan and Leonardo DiCaprio showed us in “Inception,” memories can actually be implanted so deeply into our minds that we believe them to be fully true. Although that may sound concerning, the field of law has already incorporated many of these findings in legal proceedings — polygraph examinations, DNA-testing, and corroboration between multiple, independent witnesses are standards. As our understanding of the brain advances through high-powered computing systems and better neuroimaging techniques, I am convinced that the legal field will continue to adjust accordingly. And that is not to say that you, the reader, need a university-level understanding of neuroscience; all you need is a curious, malleable mind.


[1] Cahill & McGaugh, 1996

[2] Buchanan, 2007

[3] L.M. Tran 2017, Session 522.02/UU5, Society for Neuroscience